Abstract: To investigate the efficacy of immobilized microorganism technology in remediating cadmium (Cd) contamination in red clay and its impact on environmental pollution, we conducted a series of basic physical tests, unconfined compressive strength tests, toxic leaching tests, and heavy metal extraction tests. Activated carbon served as the carrier with Bacillus pasteuri as the strain. Results revealed Bacillus pasteuri’s robust cadmium ion tolerance. Compared to either microorganism or activated carbon alone, immobilized microorganism exhibited superior remediation efficacy. Unconfined compressive strength of soil containing 14% activated carbon and microorganisms reached 229.7 kPa, a 174.4% increase over cadmium-contaminated soil. Within 21 days, cadmium leaching concentration in soil containing 10% activated carbon and microorganisms decreased to 0.002 mg/L, down by 99.8% compared to Cd-contaminated soil samples. After remediation, cadmium in soil transitioned from a weak acid state to reducible and residual states. In summary, immobilized microorganism technology demonstrates effective remediation of cadmium-contaminated red clay, particularly at a 10% activated carbon concentration. These findings offer valuable insights for addressing cadmium pollution in red clay in Guizhou Province.

Key words: red clay, Bacillus pasteurii, immobilized microbial technology, Cd contamination, soil remediation, scanning electron microscope(SEM)